Réponse:

a) (3x + 5) + (4x - 2)

= 3x +5 +4x -2

= 3x +4x +5 -2

= 7x +3

b) (10x + 3) - (4x + 8)

= 10x +3 -4x -8

= 10x -4x +3 -8

= 6x -5

c) (-9x + 1) + (4 - 5x)

= -9x +1 +4 -5x

= -9x -5x +1 +4

= -14x +5

d) (x - 7) - (4x - 3)

= x -7 -4x +3

= x -4x -7 +3

= -3x -4